CIE iGCSE Co-Ordinated Science B5. Enzymes Exam Style Questions Paper 3
Question
(a) Table 7.1 shows some information about five different enzymes.
(i) Identify the enzyme(s) from Table 7.1 that:
• have the widest pH range of activity …………………….. and ……………………..
• is active at pH 5.5 …………………………………………
• is most active in alkaline conditions. …………………………………………
(ii) State one other factor, apart from pH, that affects the activity of enzymes.
(b) Circle two words that are used to describe enzymes.
carbohydrates catalysts fats
hormones proteins solvents
(c) The list shows some parts of the alimentary canal and associated organs.
anus gall bladder mouth
oesophagus pancreas small intestine
Choose words from the list to identify where each process occurs.
Each word may be used once, more than once or not at all.
mechanical digestion …………………………………………
egestion …………………………………………
ingestion …………………………………………
(d) Describe one similarity between absorption and assimilation.
▶️Answer/Explanation
Ans : 7(a)(i) A AND C ;
A ;
C ;
7(a)(ii) temperature / AVP ;
7(b) proteins circled ;
catalysts circled ;
7(c) mouth ;
anus ;
mouth ;
7(d) both involve the movement of, digested food / molecules / soluble nutrients ;
Question
Fig. 3.1 shows four forces, A, B, C and D, acting on a submarine travelling underwater at a constant depth and at constant speed.
(a) (i) State the name of force C.
…………………………………………………………………………………………………………………….
(ii) State how the magnitude of force B compares to the magnitude of force D.
…………………………………………………………………………………………………………………….
(b) Sound above the maximum frequency that the healthy human ear can hear is called ultrasound.
The submarine stops moving and then uses ultrasound to determine the depth of the sea floor.
(i) Suggest a value for the frequency of ultrasound.
frequency = ……………………………………………. Hz
(ii) Pulses of ultrasound waves are sent out through the water. The ultrasound pulses reflect
off the sea floor and the reflection is detected by the submarine 1.4s later.
Ultrasound waves move through sea water at a speed of 1600m/s.
Calculate the total distance travelled by the ultrasound pulse.
distance = …………………………………………….. m
(iii) Use your answer to (b)(ii) to calculate the distance between the sea floor and the submarine.
distance = …………………………………………….. m
(c) The submarine is powered by a nuclear reactor.
The nuclear reactor uses the nuclear fission of the isotope uranium-235.
(i) State what is meant by the term isotope.
………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………..
(ii) Describe what happens to the nucleus of a uranium-235 atom during nuclear fission.
……………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………….
(iii) Suggest one advantage of using nuclear fission to generate electricity.
……………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 3(a)(i) weight ;
3(a)(ii) equal ;
3(b)(i) above 20 000 (Hz) ;
3(b)(ii) distance = speed × time or formula or 1600 × 1.4 ;
= 2200 or 2240 (m) ;
3(b)(iii) (answer to 3(b)(ii) ÷ 2)
= 1100 or 1120 ;
3(c)(i) atoms of the same element which have the same proton number but a different nucleon number ;
3(c)(ii) splits ;
3(c)(iii) one from:
no CO$_{2}$ emissions ;
reliability ;
AVP ;
Question
(a) Enzymes are only active within a specific pH range.
Table 7.1 shows the specific pH range for five different enzymes.
Identify the enzyme(s) from Table 7.1 that are:
only active in acidic conditions ……………………………………………..
active over the widest range of pH values ……………………………………………..
active at pH8. ……………………………………………..
(b) State one factor, other than pH, that affects enzyme activity.
…………………………………………………………………………………………………………
(c) Enzymes are proteins.
the elements that all enzymes contain.
calcium carbon chlorine hydrogen
magnesium nitrogen oxygen
(d) Table 7.2 lists some large nutrient molecules and the smaller molecules from which they are made.
Complete Table 7.2.
(e) Digested nutrients are absorbed by the body.
Place ticks (√) in the boxes to show two correct statements about absorption.
▶️Answer/Explanation
Ans: 7(a) A and D ;
C ;
B and C ;
7(b) temperature / AVP ;
7(c) carbon, hydrogen, oxygen, nitrogen circled ;
7(d)
7(e)
;;
3 ticks and 2 correct = 1 mark
3 ticks and 1 correct = 0 marks
4 or more ticks = 0 marks
Question
(a) (i) Define the term enzyme.
(ii) Fig. 10.1 is a graph showing the activity of enzyme A at different pH values.
Describe the trend shown in Fig. 10.1.
Use data in your answer.
(b) Photosynthesis and respiration are both enzyme-controlled reactions.
The table shows some features of photosynthesis and aerobic respiration.
Place ticks (3) in the boxes to show the correct features of each process.
(c) Respiration is one of the characteristics of living organisms.
State three other characteristics of living organisms.
1 …………………………………………………………………………
2 …………………………………………………………………………
3 …………………………………………………………………………
▶️Answer/Explanation
Ans : 10(a)(i) a protein ;
(that functions as) a biological catalyst ;
10(a)(ii) enzyme activity increases then decreases (with increasing pH) ;
optimum / peak / maximum activity, at pH7 ;
10(b) 
10(c) any three from:
movement ;
sensitivity ;
reproduction ;
growth ;
excretion ;
nutrition ;
Question (a)
A student writes a definition of an enzyme. The definition is not correct. ‘Enzymes are fats that function as chemical catalysts.’ Circle the two words in the student’s definition that are not correct.
The two incorrect words in the definition are fats and chemical.
▶️Answer/Explanation
Answer: The two incorrect words in the definition are fats and chemical.
Explanation: Enzymes are proteins, not fats, and they function as biological catalysts, not chemical catalysts. Enzymes speed up biochemical reactions in living organisms without being consumed in the process.
Question (b)
Enzymes are used to break down large molecules into smaller molecules. Table 10.1 shows some large molecules and the smaller molecules they are made from. Complete Table 10.1.
| Large molecules | Smaller molecules |
|---|---|
| 1. Starch | Glucose |
| 2. Glycogen | Glucose |
| Proteins | Amino acids |
| Fats | 1. Fatty acids 2. Glycerol |
▶️Answer/Explanation
Answer: The completed table is shown above.
Explanation:
- Starch and glycogen are broken down into glucose by enzymes like amylase.
- Proteins are broken down into amino acids by enzymes like proteases.
- Fats are broken down into fatty acids and glycerol by enzymes like lipase.
Question (c)
List the three chemical elements that make up fats.
▶️Answer/Explanation
Answer: The three chemical elements that make up fats are:
- Carbon
- Hydrogen
- Oxygen
Explanation: Fats are composed of carbon, hydrogen, and oxygen atoms. They are a type of lipid and are made up of fatty acids and glycerol.
Question (d)
Fig. 10.1 is a graph showing the enzyme activity at different temperatures of four different enzymes, A, B, C, and D.
Table 10.2 shows average temperatures in different environments.
(i) Describe the effect of temperature on the enzyme activity of enzyme B. Use data to support your answer.
(ii) Use Fig. 10.1 and Table 10.2 to identify the enzyme, A, B, C, or D, found in bacteria that can survive in:
▶️Answer/Explanation
Answer:
(i) Enzyme B’s activity increases as the temperature rises, reaching a peak at around 33°C, after which the activity decreases sharply. This indicates that enzyme B has an optimum temperature of 33°C.
(ii) The enzymes are:
- Hydrothermal vent regions: Enzyme D (optimum temperature around 95°C)
- Arctic seas: Enzyme A (optimum temperature around -2°C)
- The same environment as enzyme C: Enzyme D (both have high-temperature optima)
Explanation:
(i) Enzyme activity increases with temperature up to the optimum temperature, after which the enzyme denatures and activity decreases. Enzyme B’s optimum temperature is 33°C.
(ii) Enzymes have specific temperature ranges at which they function best. Enzyme D is adapted to high temperatures (hydrothermal vents), while Enzyme A is adapted to low temperatures (arctic seas). Enzyme C and D both function in high-temperature environments.